Spacers for electrical winding structures



Much 10, 1970 w. CAMPBELL ETAL 3,500,272

SPIJWERS FOR ELECTRICAL WINDING smucwunns Filed April 29, 1968 5 Sheets-Sheet 1 WITNESSES INVENTORS Lon W. Campbell and BY y Heinz G. Fischer aui M v Y I ATTORNE m K A March 1-0, 1970 ,w CAMPBELL, ETAL 3,500,272

FIG.2.

United States Patent 3,500,272 SPACERS FOR ELECTRICAL WINDING STRUCTURES Larry W. Campbell, Muncie, Ind., and Heinz G. Fischer,

Elm Grove, Wis., assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Apr. 29, 1968, Ser. No. 724,703 Int. Cl. H01f 27/08, 27/30 US. Cl. 336-60 11 Claims ABSTRACT OF THE DISCLOSURE A Winding structure for electrical inductive apparatus, including a pancake type coil and a spacer washer member. The spacer washer member includes an insulating sheet member having a plurality of substantialy triangular shaped projections arranged in a spaced uniform pattern. The spacer washer member is disposed adjacent the pancake coil, with its triangular projections against the turns thereof. The insulating sheet member and adjacent surface of the pancake coil provide a cooling duct having a plurality of tortuous paths provided by the triangular projections.

BACKGROUND OF THE INVENTION Field of the invention The invention relates generally to electrical inductive apparatus, such as transformers, and more particularly to winding structures for electrical inductive apparatus of the shell-form type.

Description of the prior art Electrical inductive apparatus, such as transformers and reactors of the shell-form type, include one or more windings, each formed of a plurality of serially connected pancake type coils. The pancake coils are disposed in spaced side-by-side relation, separated by insulating spacer washer members. The spacer washer members each include an insulating sheet member, having a plurality of rectangular insulating blocks attached thereto with a suitable adhesive. The side with the blocks attached thereto is disposed adjacent a pancake coil, with the blocks in contact with the turns of the pancake coil. The insulating sheet member and adjacent surface of the pancake coil provide a cooling duct through which a fluid cooling dielectric, such as oil, flows. The rectangular blocks space the pancake coil from the insulating sheet member, they provide a plurality of paths through which the fluid coolant flows, and they support the turns of the pancake coil and prevent them from being deformed due to short circuit forces.

The placement and gluing of the rectangular blocks on the insulating sheet member is time consuming and costly. The block pattern is not only intricate, but a different pattern is used in the curved corner sections of the washer member than in the straight sections which join the corners. Each washer member has twelve boundary lines between spacer patterns, three at each corner. The placement of the blocks at the boundary lines is left to the judgment of the assembly line operating personnel, with the changeover between patterns differing with different washer sizes. Special care must be used in placing the rectangular blocks near the washer edges, as they must not interfere with the inside and outside straight and curved channel-like insulating members, which are disposed over the edges of the pancake coils. At assembly, any interference between the channel edge members nd the spacer blocks is solved by peeling off the interfering block. Since it is diflicult to replace this block with a 3,500,272 Patented Mar. 10, 1970 "ice block of smaller dimensions, due to the difficulty in placing a smaller block between the washer and coil after assembly, they may not always be replaced, leaving a large area of the pancake coil unsupported.

The rectangular blocks cover 45-55% of the coil area, making it necessary to remove the heat from the coil from the remaining exposed area. Tests have shown that the rectangular blocks tend to distribute oil flow unevenly, with some oil flowing in relatively straight paths with very little turbulence, and thus picking up very little heat, and with the oil stagnating at other areas of very little flow. Thus, undesirable hot spots are created in the coil, which limit the overload capacity of the inductive apparatus.

SUMMARY OF THE INVENTION Briefly, the present invention is a new and improved winding structure for electrical inductive apparatus, including pancake type coils and spacer washer members, which is less costly to manufacture, and which provides more eflicent and uniform cooling of the pancake coils. The spacer washer member, instead of utilizing rectangular blocks of different sizes, disposed in a plurality of patterns, uses triangular projections or blocks disposed in a uniform pattern, on at least one side of an insulating sheet member. The triangular blocks cover less area than rectangular blocks, without deleteriously affecting the ability of the spacer washer to hold the coil turns in place during short circuit stresses, thus exposing more coil area to the coolant. Further, the triangular spacer blocks are disposed in a uniform spaced pattern of vertical, horizontal, and diagonal rows, wherein lines drawn perpendicular to any one side of the spacers, at a corner, in one row, will intersect spacers in the next adjacent row by a predetermined dimension. This overlap creates a tortuous flow path for the coolant, providing a turbulence in the coolant which removes heat more efficiently from the surface of the coil. The uniform pattern provides a uniform coolant flow across the exposed surfaces of the coil, eliminating hot spots and areas of coolant stagnation, and it makes the placement and gluing of the blocks to the insulating sheet member a simple operation for production line personnel. The pattern outline may be stamped on the insulating sheet member, eliminating judgment placement of the blocks. Further, the uniform pattern enables the triangular blocks to be pre-glued to strips of insulating material in an automatic machine, with the strips of spacers then being glued to the insulating sheet member.

BRIEF DESCRIPTION OF THE DRAWINGS Further advantages and uses of the invention will become more apparent when considered in view of the following detailed description and drawings, in which:

FIG. 1 is an elevational view, in section, of a transformer having a winding assembly constructed according to the teachings of the invention;

FIG. 2 is a perspective view of a portion of an insulating spacer washer member constructed according to the teachings of the invention;

FIG. 3 is an elevational view of a portion of an insulating spacer washer member constructed according to another embodiment of the invention; and

FIGS. 4, 5, 6 and 7 are plan views of spacer block members constructed according to still other embodiments of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings, and FIG. 1 in particular, there is shown electrical inductive apparatus 10 constructed according to the teachings of the invention. Inductive apparatus 10, which may be a transformer or a reactor, includes a coil-winding assembly 12 disposed in a tank or casing 14, which is filled to a suitable level 16 with a cooling and insulating dielectric fluid, such as oil. Casing 14 may have suitable inlet and outlet openings 18 and 20, respectively, connected to external heat exchanger means (not shown) for circulating and cooling the dielectric fluid. The dielectric fluid is heated by the core-winding assembly 12 and rises, thus establishing a natural upward flow of the coolant, as illustrated by the arrows in FIG. 1, due to the thermal siphon effect. Pumps (not shown) may be added to force the coolant to flow through the coil-winding assembly 12 and through the external heat exchanger means, if required.

The core-winding assembly 12 is of the shell-form type, and may be single or polyphase. The core-winding assem-' bly 12 includes magnetic core sections 22 and 24, which comprise a plurality of stacked metallic laminations 26, formed of a suitable magnetic material, such as grain oriented silicon steel. Magnetic core sections 22 and 24 are disposed in side-by-side relation, with their adjacent portions forming a winding leg for the winding assembly. Core-winding assembly 12 also includes a winding assembly, shown generally at 30, which is disposed in inductive relation with magnetic core sections 22 and 24. If inductive apparatus is a transformer, it will include high and low voltage windings, which may be of the isolated type, or of the autotransformer type.

Electrical winding assembly 30 includes a plurality of discs or pancake type spirally wound coils, such as pancake coil 32, which has an opening 34 for receiving the leg portions of core sectionn 22 and 24. The plurality of pancake coils are stacked in side-by-side relation, with their openings or windows in alignment. The pancake coils of each separate winding are serially connected with startstart, finish-finish connections, in a manner well known in the art.

Each pancake coil, such as pancake coil 32, has a plurality of turns 36 formed of an insulated electrical conductor, such as copper or aluminum, with the conductor having one or more conductive strands, as required by the particular application. Each pancake coil has two major opposed surfaces, perpendicular to the opening 34, which are joined by the opening or the inner edge of the coil, and by its outer edges. Asillustrated, the pancake coils are generally rectangular in shape, having four straight sections, joined by four rounded outer corners.

Each of the pancake coils have a plurality of tight fitting insulating channel members applied to both its inner and outer edges, to insulate and accommodate the high electrical stresses at the edges of a coil. For example, pancake coil 30 has a plurality of insulating channel members 38 applied end-to-end to completely cover its inner edge, and a plurality of insulating channel members 40 applied end-to-end to completely cover its outer edge.

Cooling ducts adjacent the major surfaces of each pancake coil are formed by insulating washer members which include a plurality of insulating spacer blocks having one surface in contact with a major surface of a pancake coil, i.e., against the conductor turns 36 of the pancake coil, and which have their opposite surface attached to an insulating sheet member, which has the same general shape as the pancake coils.

Specifically, the major surface 42 of pancake coil 32 is cooled by a duct formed by washer member 43, which includes a plurality of spacer blocks 44 attached to a sheet insulating member 46, such as by gluing. The blocks 44 and sheet insulating member 46 may be formed of any suitable insulating material, such as pressboard.

The pancake coil adjacent pancake coil 32, in the cut away portion of the inductive apparatus 10, is cooled via a duct formed by washer member 49, which includes insulating sheet member 48 and a plurality of spacer blocks 50. Spacer blocks 50 are glued to one of the major surfaces of insulating sheet member 48, and its other major surface is disposed against the major surface of insulating sheet member 46 which does not have the blocks attached thereto. Or, as an alternative, instead of disposing the major surfaces of two insulating sheet members together, and attaching spacer blocks to their remaining exposed major surfaces, a single spacer washer may be used which includes a single insulating sheet member having a plurality of spacer blocks attached to both of its major opposed surfaces.

Spacer blocks 44 and 50 are triangular in shape, and they are disposed in a uniform pattern. As illustrated in FIG. 2, which is a perspective view of a portion of the insulating spacer washer member 49 shown in FIG. 1, the triangular spacer blocks 50 may be equilateral triangles disposed in vertical, horizontal and diagonal rows. All of the triangular spacer blocks are similarly oriented. The spacer blocks 50 are uniformly spaced from one another, with the distance between the geometric centers of adjacent blocks being uniform. Thus, as shown by the dotted circles, a circle drawn using the geometric center of one block as the center of the circle, will intersect the geometric centers of all of the immediately adjacent blocks. In other words, the vertical placement of the blocks is staggered from row to row, with the blocks in alternate vertical rows being aligned horizontally and the blocks in the remaining vertical rows being aligned horizontally. The geometric centers of the blocks in any aligned horizontal row fall on an imaginary line which is half way between the lines which intersect the geometric centers of the horizontal rows immediately above and immediately below the selected row.

It has been found that arranging the blocks 50 such that the generally upward direction of the coolant flow will strike one of the sides of the blocks in a substantially perpendicular manner, provides the most efficient cooling. Thus, as shown by the arrows in FIG. 2, the coolant strikes the side of the blocks disposed perpendicular to the upward flow direction of the coolant, such as side 54 of block 52, creating a turbulence and therefore a scrubbing action which provides a highly eflicient transfer of heat from the coil surface to the coolant. After striking the perpendicularly disposed sides of each of the blocks, the coolant divides into a plurality of paths to flow around the obstructing blocks.

The next important criterion in the block pattern is the spacing between the blocks. If they are spaced too far apart, straight perpendicular paths will be provided between the vertical rows of blocks. Most of the coolant will flow in these paths, and very little coolant flow will be provided beneath the blocks. This is undesirable, as hot spots will be created in the areas of reduced coolant flow, and the lack of turbulence in the straight through vertical paths will not provide the most eflicient heat transfer. Nor should the blocks be placed too close, as they will unduly obstruct the coolant flow. It has been found that when using triangular blocks having a dimension of approximately two inches on a side, an overlap between rows of A to /8 of an inch is desirable. This overlap is shown in FIG. 2, and is uniform in every direction. This is accomplished by spacing the blocks from one another in the vertical rows by the same dimension between the blocks in adjacent diagonal rows. The corners of each of the blocks point to the center of the sides on adjacent blocks. Thus, the dimension between the corners of the blocks and the sides of the blocks adjacent to the corners, is uniform. The dimension between blocks is established by determining the overlap between vertical rows which is desirable, and then measuring the distance between the corners of the blocks and the immediately adjacent sides of other blocks between the vertical rows. This distance will then be used to establish the spacing between the blocks in the vertical rows. This over-lapping may be demonstrated by drawing straight dotdash lines through all like corners of rows, perpendicular to the sides of the triangular spacers. Thus, line 56 may be drawn which is perpendicular to the bottom sides of the spacers in the first vertical row, and which intersects the lower right corners of the blocks, and line 58 may be drawn, which is perpendicular to the bottom sides of the spacers in the second vertical row, and which intersects the lower lefthand corners of these blocks. The dimension 60 between lines 56 and 58 indicates the block overlap between vertically disposed rows. In like manner, lines 62 and 64 may be drawn perpendicular to the left-hand sides of the blocks intersecting the upper corners of the blocks in one diagonal row, and the lower left-hand corners of the blocks in the next adjacent higher diagonal row, illustrating an overlap 66 between the diagonal rows which slope downwardly from left to right, with this overlap having the same dimension as that of overlap 60. Lines 68 and 70 may be drawn perpendicular to the right-hand sides of the blocks, intersecting the upper corner of the blocks in one diagonal row, and the lower right-hand corner of the blocks in the next adjacent higher diagonal row, illustrating an overlap 72 between the diagonal rows which slope upwardly from left to right, which overlap has the same dimension as that of overlaps 60 and 66.

The overlaps between the vertical rows and between the diagonal rows, break up straight flow paths and create tortuous paths for the coolant, always directing the coolant into the sides of the triangular blocks which are disposed perpendicularly to the upward flow of the coolant, and thus creating a similar turbulence below each triangular block.

The importance of block orientation may be readily visualized by assuming that the coolant flow was in a direction opposite to that shown by the arrows in FIG. 2. The coolant would never strike a block side perpendicularly, but would merely flow along the sides of the blocks. There would be very little flow of the coolant along the sides of the blocks which are parallel to the side 54 of block 52.

Thus, it is important that the triangular blocks be oriented such that one of the sides of each of the blocks is substantially perpendicular to the upward flow of the coolant, such that the coolant strikes the side in a substantially perpendicular manner, and it is important that the blocks be staggered vertically from vertical row to vertical row, to allow an overlap between the rows to be provided which directs the coolant into the sides of the blocks disposed perpendicularly to the direction of the coolant flow.

An insulating spacer washer was constructed according to the teachings of the invention, using triangular blocks formed of pressboard having a dimension of two inches on a side, and a thickness dimension of inch, with these blocks being glued to an insulating sheet member formed of inch thick pressboard. The geometric centers of the triangular blocks were placed on two inch centers, and an overlap between the vertical and diagonal rows of one-quarter inch was used. A transparent cover was placed over the projecting triangular spacers, which simulated the pancake coil, and a colored coolant was formed to flow through the resulting duct, such that the coolant would strike one of the sides of each of the ducts in a substantially perpendicular manner. The coolant flow was uniform about all sides of the spacer blocks. A washer member was also constructed according to the teachings of the prior art, using rectangular spacer members disposed in prior art patterns, a transparent cover was placed over the projecting rectangular spacers, and a colored coolant was forced to flow in the resulting duct. Here it was observed that definite flow paths were set up, which left approximately 50% of the exposed coil area inadequately cooled. Most of the coolant flowed in these definite flow paths, without turbulence, with the areas outside of these flow paths containing stagnated coolant. Using rectangular spacers, approximately 45 to 55% of the coil surface is covered by the spacers, which means that only about 25% of the coil area is properly ventilated 6 due to active coolant flow in only 50% of the exposed coil area. Using triangular spacers, only 40 to 41% of the coil surface is covered with the spacers, and substantially all of the exposed coil surface is well ventilated.

The reduction in the percentage of the coil surface covered by the triangular spacers, compared with the prior art rectangular spacers, does not reduce the effectiveness of the washer in holding the coil turns during short circuit stresses. The uniformly placed triangular spacers uniformly support the coil turns, with no chance of some coil areas being unsupported, such as due to poor judgment by assembly line personnel in placing rectangular blocks, or due to block removal due to blocks which interfere with the channel insulating members. With the uniform pattern, the pattern print may be placed on the insulating sheet member, with the pattern taking into account the locations of the insulating channel members on the coil edges.

As shown in FIG. 2, the blocks 50 may be discrete blocks secured to the insulating sheet member 46, such as with a suitable adhesive. Instead of using discrete blocks 50, the blocks 50 may be triangular projections formed integrally with the sheet member 46. They may project outwardly from a backing member of uniform thickness. Or, the integral projections may be formed by pressing the insulating sheet material between suitable dies, while the sheet material is in a semiplastic stage. This may be accomplished either during the manufacturing of the pressboard, or it may be subsequently softened with a suitable softening process, such as by soaking the insulating sheet member in water prior to the forming step.

Another method of attaching the triangular spacer block members to a sheet of insulating material is shown in FIG. 3, which is an elevational view of a portion of an insulating washer member 80. Insulating washer member includes an insulating sheet member 82, and a plurality of triangular block members 84. However, instead of gluing the blocks 84 directly to the insulating sheet member 82, they are pre-glued on a thin strip of insulating material, such as strips 86, 88 and 90. The gluing of the triangular blocks to the thin strips of insulating material may be automated, with the spacer blocks being automatically glued to the strips at the time the triangular spacer blocks are manufactured. In order to provide the desired overlap dimensions between the vertical and diagonal rows, strips 86, 88 and 90 may have a width dimension narrower than the dimensions of one of the sides of the triangular blocks, or the strips may be scalloped as shown in FIG. 3. Scalloped strips have the advantage of automatically aligning the blocks from row to row, and thus providing the required stagger between the rows, by merely fitting the scalloped edges together. The strips 86, 88 and 90 are cut to length and glued to the insulating sheet member 82.

While the preferred embodiment of the invention utilizes spacer blocks having the shape of equilateral triangles, it is to be understood that the invention, in general, applies to projections having a substantially triangular configuration, i.e., projections having three outer corners. For example, FIG. 4 illustrates a spacer block 94, having sides and 96 whose dimensions are equal to each other, but shorter than the dimension of side 97. Thus, the spacer block members may be isosceles, if desired, with the oil flow being directed against side 97, as illustrated by the arrows.

In an effort to reduce the amount of coil surface covered by the blocks, and thus provide more coil surface from which heat may be removed, the triangular blocks may have cut-out portions which reduce their surface area without substantially impairing their ability to support the coil turns during short circuit stresses. For example, FIG. 5 illustrates a spacer block member 100 which has a triangular opening 102 out in the side which faces the oil flow, illustrated by the arrows, which side is substantially perpendicular to the oil flow direction. This cut-out portion in the spacer block members will create even more turbulence in the oil flow.

FIG. 6 illustrates a spacer block member 104 having triangular openings 104 and 106 on the two sides thereof which are inclined in the general direction of the oil flow, and FIG. 7 illustrates a spacer block member 110 having triangular openings 112, 114 and 116 in its three sides, respectively.

Other substantially triangular shapes that would be suitable are triangular spacer block members having one or more concave or convex sides.

In summary, there has been disclosed a new and improved winding structure, including pancake type coils and insulating spacer washer members disposed between the coils, with the latter providing mechanical support for the coil turns, and creating ducts adjacent the coil surfaces for removing heat therefrom. The insulating spacer washer members include an insulating sheet material having a plurality of triangular projections which extend outwardly from at least one side thereof, in a predetermined uniform pattern, which provides the desired mechanical support for the coil turns while covering less coil surface than prior art washer members. The triangular spacer block projections also substantially improve the ventilation of the coils, compared with the rectangular spacer block porjections of the prior art. Hot spots in the coils are eliminated by the triangular spacer block members, due to the substantially uniform flow of the cooling fluid over the exposed coil surfaces, and due to the turbulence in the coolant as it flows through the tortuous paths provided by the triangular spacers. In addition to improving the ventilation of the coils, the manufacturing of the insulating washer members is facilitated, as only one block pattern is required for each washer. The block pattern is based on the centerline of the washer, and is not affected by the size of the washer. Further, only one block size is required. The uniform pattern and uniform size of the blocks facilitates automation in the laying of the blocks on an insulating sheet member, allows the blocks to be pre-glued to thin insulating strips and subsequently glued to an insulating sheet member, and it allows the blocks to be in the form of integral projections which extend outwardly from at least one side of an insulating sheet material. If the triangular spacer blocks are to be manually placedon an insulating sheet material, the pattern may be pre-printed on the insulating sheet, thus saving time in the placement of the blocks and reducing errors in their placement.

Since numerous changes may be made in the above described apparatus and different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative, and not in a limiting sense.

We claim as our invention:

1. A winding assembly for fluid cooled electrical inductive apparatus, comprising:

at least one pancake coil having a plurality of conductor turns,

at least one spacer washer member, including a sheet insulating member having a plurality of triangularly shaped projections extending outwardly from at at least one side thereof, in predetermined spaced relation,

said plurality of triangular projections being disposed in a plurality of rows, with the projections of adjacent rows being offset from one another such that the corners of the projections in each row intersect a line drawn between like corners of projections in adjecent rows,

said spacer washer member being disposed adjacent said at least one pancake coil, with its triangular projections in contact with the conductor turns thereof, to provide mechanical support for said turns,

and to provide a duct, defined by said insulating sheet member and said pancake coil, having a plurality of tortuous paths therethrough,

said triangular projections being oriented such that the cooling fluid directed through the duct will strike one of the sides of each of said triangular projections in a direction which is substantially perpendicular thereto.

2. The winding assembly of claim 1 wherein the triangular projections are an integral part of the insulating sheet member.

3. The winding assembly of claim 1 wherein the triangular projections are discrete blocks, and including means for attaching said blocks to the insulating sheet member.

4. The winding assembly of claim 1 wherein the triangular projections are substantially equilateral in shape.

5. The winding assembly of claim 1 wherein the triangular projections are arranged with an equal spacing between the geometric center of any one projection and the geometric centers of the immediately adjacent projections.

6. An insulating washer member for spacing pancake coils in electrical inductive apparatus, comprising:

an insulating sheet member having a plurality of substantially triangular projections extending outwardly from at least one side thereof,

said triangular projections being disposed in a plurality of rows, and oriented such that cooling fluid directed in a direction parallel to the side of the insulating sheet member will strike one of the sides of each of the triangular projections in a substantially perpendicular manner,

said triangular projections in adjacent rows being offset from one another, with the corners of the projections in each row intersectiing a line drawn between like corners of projections in adjacent rows, by a predetermined dimension, to provide tortuous paths for coolant between the triangular projections.

7. The insulating washer member of claim 6 wherein the triangular projections are an integral part of the insulating sheet member.

8. The insulating washer member of claim 6 wherein the triangular projections are discrete block members, and including means attaching said discrete block members to the insulating sheet member.

I 9. The insulating washer member of claim 6 wherein the triangular projections are substantially equilateral in shape.

10. The insulating washer member of claim 6 wherein the triangular projections are arranged with an equal spacing between the geometrical center of any projection and the geometrical centers of the immediately adjacent projections.

11. The insulating sheet member of claim 6 wherein said triangular projections are discrete block members attached to a plurality of strips of insulating material, and including means attaching said plurality of strips to said insulating sheet member.

References Cited UNITED STATES PATENTS 2,677,792 5/1954 Wright 33618S FOREIGN PATENTS 715,677 8/1965 Canada.

1,278,093 .10/1961 France.

404,741 of 1943 Italy.

THOMAS J. KOZMAN, Primary Examiner US. Cl. X.R. 336 

